A class of inflation models with non-minimal coupling

We show that the potential of the scalar field in the Einstein frame is flat if the nonminimal coupling term is properly chosen that it satisfies the condition (V(phi)/K^2(phi)-> constant) as phi gets large. The cosmological implication of this theory is studied.Comment: Talk at the international Workshop on e-Science for Physics 2008 during September 8-9, 2008 at Daejeon Convention Center, Daejeon, Kore

Critical comment on the recent microscopic black hole search at the LHC

Recently the CMS collaboration at the LHC reported "the first direct limit on black hole production at a particle accelerator" using a data sample corresponding to an integrated luminosity of 35/pb of pp-collision at a center of mass energy of 7 TeV. Even though the result has a strong impact on future searches, the interpretation lacks enough theoretical support. In this letter, we show that the parameter range which was considered by the CMS collaboration is actually out of the validity range of semi-classical black hole picture so that the Monte-Carlo simulation result which was crucially used in the analysis still needs further solid scientific basis.Comment: 5 pages, 3 figures, version to appear in PL

A testable scenario of WIMPZILLA with Dark Radiation

As the electromagnetic gauge symmetry makes the electron stable, a new abelian gauge symmetry may be responsible for the stability of superheavy dark matter. The gauge boson associated with the new gauge symmetry naturally plays the role of dark radiation and contributes to the effective number of `neutrino species', which has been recently measured by Planck. We estimate the contribution of dark radiation from the radiative decay of a scalar particle induced by the WIMPZILLA in the loop. The scalar particle may affect the invisible decay of the Higgs boson by the Higgs portal type coupling.Comment: 4 pages, 3 figure

Radiatively decaying scalar dark matter through U(1) mixings and the Fermi 130 GeV gamma-ray line

In light of the recent observation of the Fermi-LAT 130 GeV gamma-ray line, we suggest a model of scalar dark matter in hidden sector, which can decay into two (hidden) photons. The process is radiatively induced by a GUT scale fermion in the loop, which is charged under a hidden sector U(1), and the kinetic mixing ($\sim \epsilon F^{\mu\nu}F'_{\mu\nu}$) enables us to fit the required decay width for the Fermi-LAT peak. The model does not allow any dangerous decay channels into light standard model particles.Comment: 15 pages, 6 figures, Discussion on the morphology of 130 GeV gamma-rays: decay vs annihilation, references adde

Hyperbolic Inflation

We propose a natural scenario for the cosmological inflation with the non-minimal coupling term invoking compact hyperbolic extra dimensions. Thanks to the unique mathematical properties of compact hyperbolic space, the large volume of extra dimensions, which provides a natural understanding of the proper size of couplings, does not necessarily accompany with the low Kaluza-Klein scale so that the model allows a single field inflation with a scale around $10^{13}$ GeV. The model fulfills all the observed data and predicts a sizable gravitational perturbation, r~0.003.Comment: 5 page

Dark Matter and Collider Physics in Split-UED

Kaluza-Klein dark matter is an attractive weakly interacting massive particle in universal extra dimension model. In the recent extension "split-UED", annihilation of Kaluza-Klein dark matter with a mass range 600-1000 GeV provides excellent fits to the recently observed excesses in cosmic electron and positron fluxes of Pamela, ATIC and Fermi-LAT experiments. The cosmic gamma-ray flux in the same process can be significant around 300 GeV, thus can be observed or constrained by the forthcoming Fermi-LAT diffuse gamma-ray data. The collider signal at the LHC is the resonance in the dijets channels and the large missing energy in the missing energy plus jets.Comment: 3 pages, 6 figures, Talks given at 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY09), Boston, USA, 5-10 June 200

Split-UED and Dark Matter

Motivated by the recent observation of the high energy electron and positron excesses in cosmic ray by PAMELA and ATIC/PPB-BETS, we suggest an anomaly-free scenario for the universal extra dimension that localizes the SM quarks and splits the spectrum of KK quarks from KK leptons. When the SM quarks are "well localized" at the boundaries, the most stringent bound of the model ($1/R > 510$ GeV) comes from the resonance search for the Tevatron dijet channels. Even at the early stage of LHC, one can discover the second KK gluon for masses up to 4 TeV.Comment: 4 pages, 3 figures, 1 tabl